The debate over the effects of head injuries sustained by NFL players intensified on Sunday after three quarterbacks, two defensive ends and a tight end suffered game-ending concussions.

The three quarterbacks – Michael Vick of the Philadelphia Eagles, Jay Cutler of the Chicago Bears and the San Francisco 49ers' Alex Smith – suffered concussions in their matches against the Dallas Cowboys, the Houston Texans and the St Louis Rams. Brandon Myers, an Oakland Raiders tight end, suffered his second concussion of the season in a heavy defeat by the Baltimore Ravens; the Detroit Lions defensive end Cliff Avril was concussed in a defeat by the Minnesota Vikings; and the Bears defensive end Shea McClellin was also hurt.

The NFL's injury round-up also said that the Buffalo Bills running back Fred Jackson had suffered a non-specified head injury during his team's defeat by the New England Patriots. It quoted the Bills head coach, Chan Galley, as saying: "I don't know if they're calling it a concussion. I don't know what the word is. I don't know if it's a concussion or not. They didn't tell me."

Among its reports of calf, ankle and other lower-body injuries, the NFL also said that the Tampa Bay Buccaneers linebacker Quincy Black had been taken to hospital after suffering a neck injury during his team's win over the San Diego Chargers. The NFL said he would undergo tests for spinal or neurological damage.